For years I was confused about this. Why would you want to be richer i.e. give the engine more fuel on a cold day compared to a hot day!
But when you start to think about it in terms of air density then it starts to make sense. It's not about needing to richen the engine on a cold day per se.
Yes you need to screw the jets out on a cold day but it's to balance the fact that the air is more dense and so relative to a warmer day when air is less dense, less fuel can get through. So the richening on a cold day is more about balancing the air and fuel to give the engine it's optimal mix of fuel and air, not necessarily "richening" it.
The same principal applies when you have high or low pressure. When the pressure is high you will need to have "richer" jetting compared to when there is low pressure. Air pressure will affect your jetting whether it's winter or summer.
I hope this helps.
|
|